When you think of animals carrying fleas, what comes to mind are dogs and cats, a problem that most responsible pet owners know all about.

But an equal, yet lesser known threat is lurking in the wild and unbeknownst to homeowners, living under the floorboards or in the attic. We are talking about opossums.

Grumpy baby opossums are cared for by volunteers at the Wetlands and Wildlife Care Center in Huntington Beach on Saturday, May 5, 2018. (Photo by Mindy Schauer, Orange County Register/SCNG)

In fact, the opossum was named by public health officials this past week as a main carrier of fleas that transmit typhus fever. The opossum, or possum, is a major contributor to the outbreak in Pasadena, where a record 20 cases have been reported this year as of Thursday, an “elevated level” well above the average of one to five cases per year, according to the city of Pasadena.

Los Angeles County is reporting 59 cases of typhus fever so far this year. Of those, nine are associated with an outbreak in downtown Los Angeles and six of those were among people experiencing homelessness, however specific outbreak locations are being withheld by the county. L.A. County Department of Public Health reported on Wednesday that about 60 cases per year is average, so the county is ahead of its yearly rate.

Long Beach has had 12 cases of flea-borne typhus, according to a city advisory in September. Both Long Beach and Pasadena cases are not included in the Los Angeles County health department total.

Fleas hosted by these animals can carry one of two strains of bacteria, Rickettsia typhi or Rickettsia felis, that cause typhus fever when they bite humans or simply land on human skin and deposit feces that get rubbed into the body and enter the bloodstream. The L.A. County health department reported the carriers are feral cats, infected rats and opossums, in an emailed response to questions on Wednesday

The disease can cause high fever, chills, headaches and rash. Typhus is fatal in only about 1 percent of the cases, according to the county health department.

“Typhus fever is a disease that can cause serious complications requiring lengthy hospitalization, and rarely, death,” said Dr. Ying-Ying Goh, Pasadena’s health officer, in a city announcement dated Oct. 5.

The disease, also known as murine typhus, responds well to treatment, mostly antibiotics, said Michael Johnson, director of the Pasadena Public Health Department during a phone interview Wednesday. Johnson said all 20 victims are recovering. “I don’t believe any are still hospitalized, although some of them were,” he said.

He said the cases are spread throughout the city of Pasadena, from the foothill neighborhoods to the central core to the more residential southern sections. He said more study needs to be done as to why there has been a jump in the number of typhus fever cases this year.

Fleas can come from pets inside a home and from possums moving through neighborhoods from wilderness areas, he said. “It is an endemic problem, But the opossum is very much a part of the problem.”

A single opossum can carry as many as 700 fleas, said Levy Sun, public information officer with the San Gabriel Valley Mosquito & Vector Control District. “If you were to capture an opossum, you would see it has a very heavy flea load.”

He has received an uptick in calls, including some from worried Pasadena residents who want to see the opossums killed and the fleas sprayed with insecticides. Both are not practical options, he said.

It is not possible to keep up with the flea population, he said. One female lays up to 50 eggs that hatch into mature adults in about two weeks.

Kimra Hines is one of the trappers who works for All Star Animal Trapping in Los Angeles. (courtesy photo)The technician from All Star Animal Trapping caught this opossum in a house in Glendale in June. The animal was found hiding between a window and a screen. (courtesy photo).

Robert Messersmith, owner of All Star Animal Trapping, serving the greater Los Angeles region, says trapping opossums is the third-most logged call, with raccoons first and skunks second.

When he finds any of these animals, he’s often covered in fleas, he said. Messersmith said a meeting was planned for Thursday “to figure out how to take better precautions.”

He said opossums, the only North American marsupials, are very prevalent in urban communities because they have no living predators. Opossums are typically 2-feet long and eat just about anything, from worms to garbage to pet food. They can employ a defense tactic by “playing dead,” which is really entering a coma-like state for up to two hours. They are nocturnal, meaning they sleep during the day and forage for food at night.

The No. 1 cause of death is being hit by a car, Messersmith said. When he traps them, he’ll drive them 10 miles outside the area and then let them go. Only injured animals can be euthanized under the law, he said.

The best way to avoid getting typhus fever is to reduce exposure to fleas. Experts recommend the following actions:

• Reduce vegetation on a yard’s perimeter, where opossums or feral cats can hide

• Fill in holes in eaves, crawlspaces or sheds

• Don’t leave cat or dog food outside

• Pick up fruit from trees

• Keep garbage containers tightly covered

• Use flea control medication on your pets

For more information, go to www.sgvmosquito.org/flea-borne-typhus.

Pasadena residents can report suspected or confirmed cases of typhus to the city health department at: 626-744-6089 (Monday through Friday from 8 a.m. to 5 p.m.) or 626-744-6043 after hours.

Steve Scauzillo covers environment and transportation for the Southern California News Group. He has won two journalist of the year awards from the Angeles Chapter of the Sierra Club and is a recipient of the Aldo Leopold Award for Distinguished Editorial Writing on environmental issues. Steve studied biology/chemistry when attending East Meadow High School and Nassau College in New York (he actually loved botany!) and then majored in social ecology at UCI until switching to journalism. He also earned a master's degree in media from Cal State Fullerton. He has been an adjunct professor since 2005. Steve likes to take the train, subway and bicycle – sometimes all three – to assignments and the newsroom. He is married to Karen E. Klein, a former journalist with Los Angeles Daily News, L.A. Times, Bloomberg and the San Fernando Valley Business Journal and now vice president of content management for a bank. They have two grown sons, Andy and Matthew. They live in Pasadena. Steve recently watched all of “Star Trek” the remastered original season one on Amazon, so he has an inner nerd.